Epoxy esters of 1, 2, 4-cyclopentanetricarboxylic acid



United States Patent:

3,057,880 EPOXY ESTERS F 1,2,4-CYCLOPENTANE- TRIQAREGXYLIC ACID John W.Lynn, Charleston, Richard L. Roberts, Milton,

and Samuel W. Tinsley, South Charleston, W. Va., assignors to UnionCarbide Corporation, a corporation of New York No Drawing. Filed May 22,1959, Ser. No. 814,993 2 Qiaims. (Q1. 26tl348) structure. By the termoxirane-containing alicyclic radical is meant an alicyclic radicalhaving the carbon atoms of at least one oxirane group incorporated aspart of the alicyclic ring to form a bicyclo structure, e.g.,

A preferred class of esters of this invention are those corresponding tothe general formula R R R0i0-iJ- JHO0iR a 4 GHCH-GO2R R1 in wherein R isa member selected from the group consisting of hydrogen and lower alkylradicals containing be tween one and about four carbon atoms; wherein Ris an aliphatic radical and at least one R is an oxirane-containingalicyclic radical, and the total number of carbon atoms in said Rradicals is between seven and about sixty carbon atoms.

Particularly preferred epoxy alicyclic esters corresponding to the abovegeneral formula are those in which the aliphatic radical R is a memberselected from the group consisting of alkyl radicals containing betweenone and eighteen carbon atoms, alkenyl radicals containing between twoand eighteen carbon atoms, cycloalkyl and cycloalkenyl radicalscontaining between six and eighteen carbon atoms, and at least one R isa cyclohexene oxide radical and the total number of carbon atoms in saidR radicals is between nine and forty-eight carbon atoms. These epoxyesters can contain halogen atoms and are further characterized as beingfree of acetylenic unsaturation.

The terms cycloalkyl and cycloalkenyl as used .herein includecycloalkylalkyl, cycloalkylalkenyl, cycloalkenylalkyl andcycloalkenylalkenyl radicals. By the term cyclohexene oxide is meant thebicycle structure ice The previously described general formula is meantto include triesters of l,2,4-butanetricarboxylic acids which have thenumber one and number four carbon atoms of the acid moiety connected bya methylene group as illus trated by the following structure wherein Rand R areas defined hereinabove.

illustrative of preferred epoxy alicyclic esters are those in which R ismethyl, ethyl, propyl, isopropyl, butyl, isobutyl and the like; and R ismethyl, vinyl, ethyl, allyl, propyl, isopropyl, butyl, Z-butenyl,isobutyl, tertiarybutyl, amyl, hexyl, 2-hexenyl, 2-ethyl-2-hexenyl,2-ethylhexyl, heptyl, octyl, 2-octenyl, nonyl, decyl, dodecyl, tridecyl,octadecyl, 9-octadecenyl, cyclopentyl, 2-cyclopentenyl, cyclohexyl,cycloheptyl, cyclohexyhnethyl, lcyclohexenyl, 2-cyclol1exenyl,S-cyclohexenyl, 4-cyclohexenyl, 3-cyclohexenylmethyl,1-methyl-3-cyclohexenylmethyl, 4-methyl-3-cyclohexenylmethyl,6-methyl-3-eyclo hexenylmethyl, 3 cyclohexenylethyl, 3cyclohexenylpropyl, 3-cyclohexylpropenyl, and the epoxy derivatives ofthe foregoing unsaturated radicals wherein the double bond is convertedinto an oxirane group, e.g., 2,3-epoxypropyl; 3,4-epoxycyclohexylmethyland the like. Typical preferred epoxy alicyclic esters include3,4-epoxycyclohexyl 'bis(methyl) 1,2,4-butanetricarboxylate; bis(3,4-epoxycyclohexylmethyl) vinyl 1,2,4-butanetricanboxylate;3,4-epoxycyclohexylmethyl bis(2-ethylhexyl) 1,2,4-butanetricarboxylate;3,4-epoxycyclohexyl bis(oxo decyl)1,2,3,4-tetrachloro-1,2,4-butanetricarboxylate; 2,3-epoxycyclohexylmethyl bis(cyclohexylmethyl) 1,2,4-butanetricarboxylate;2,3-epoxycyclopentyl *bis(2-ethylhexyl) 1,2,4- butanetricarboxylate;tris(3,4-epoxycyclohexyl) 1,2,4- butanetricarboxylate;4,5-epoxycyclohexy1 bis(9-octadecenyl) l,2,4-hutanetricarboxylate;tris(3,4-epoxycyclohexylmethyl) 1,2,4-butanetricarboxylate;tris(2,3-epoxy cyclohexyl) l,2,4-butanetricarboxylate;tris(3,4-epoxycyclohexylmethyl) 1,2,4-cyclopentanetricarboxylate, andthe like.

The epoxy alicyclic esters of this invention are readily prepared by theepoxidation of the corresponding olefinic esters. Preferred epoxidationmethods involve the use of peracetic acid or acetaldehyde monoperacetateas the epoxidizing agent.

Epoxidation employing acetaldehyde monoperacetate proceeds asillustrated in the following equation with tris(3-cyclohexenylmethyl)1,2,4=butanetricarboxy1ate as the olefinic starting material 3Epoxidation employing peracetic acid proceeds as illustrated in thefollowing equation with 2-cyclohexenyl -bis(2- ethyl-2-hexenyl)1,2,4-butanetricarboxylate as the olefinic starting material Thesuitable olefinic ester starting materials which are epoxidized toproduce the novel epoxy esters of this invention are readily prepared byconventional esterification and transesterification methods fromappropriate aliphatic alcohols and 1,2,4-butanetricarboxylic acids. Inone direct esterification method, an alcohol such as3-cyclohexen-l-methanol is reacted with a polycarboxylic acid such asl,2,4-butanetricarboxylic acid in the presence of a strong acid catalystsuch as para-toluenesulfonic acid with the continuous removal of wateras an azeotrope with an entraining agent such as benzene or toluene. Inanother direct esterification method, the alcohol is reacted with thetricarboxylic acid in the form of its acid halide derivative in thepresence of an acid-binding substance such as pyridine. In atransesteritication method, an alcohol such as 2-cyclopentenol isreacted with an ester derivative such as triethyl1,2,4-butanetricarboxylate in the presence of a catalyst such astetraalkyl titanate with the continuous removal of the replaced alcohol(e.g., ethanol) as a solitary distillation component or as an azeotropewith toluene or a similar entraining agent. The quantities of acid andalcohol reacted may be varied over broad molar ratios but it is usuallypreferred to employ either stoichiometric quantities of acid and alcoholor a small molar excess of alcohol. For example, for the preparation ofan ester which has three similar alcohol moieties, an unsaturatedalicyclic alcohol is reacted with the 1,2,4-butanetricarboxylic acid inthe ratio of three moles of alcohol for each mole of tricarboxylic acid.In the case of an ester which has dissimilar alcohol moieties, therespective alcohols are employed in the appropriate ratio. For example,when three different alcohols are to be reacted with a1,2,4butanetricarboxylic acid, a ratio of one mole of each of thealcohols is employed for each mole of tricarboxylic acid. The alcoholscan be reacted individually with the tricarboxylic acid, or the alcoholscan be reacted simultaneously as a single mixture with the tricarboxylicacid. In either case, an equilibrium reaction product is formed.

The epoxy alicyclic esters of this invention can also be prepareddirectly by the interaction of suitable epoxy aliphatic alcohols with1,2,4-butanetricarboxylic acid derivatives. This method is not preferredbecause of the various side reactions that can occur.

The class of 1,2,4-butanetricarboxylic acids useful for the productionof the novel esters of this invention are available by severalpreparative routes which are reported in the chemical literature. Forexample, 1,2,4-butanetricarboxylic acid can be prepared by the Michaelcondensation of methylenesuccinic acid ester with malonic ester, or bythe condensation of acrylonitrile with 1,1,2- ethanetricarboxylic acid.A preferred method of preparing 1,2,4-butanetricarboxylic acids is bythe nitric acid CgHs oxidation of cyclohexene derivatives correspondingto the formulas a a a H X H X 1 and R H wherein X is a carboxyl group ora group convertible to a carboxyl group such as cyano, keto and amidogroups, and R is hydrogen or a lower alkyl group containing between oneand four carbon atoms. The appropriate cyclohexene derivatives, in turn,are prepared by the Diels- Alder reaction of butadiene and othercompounds of the conjugated diene series with mono-olefinic dienophileshaving the double bond in a position vinyl to a carboxyl group or agroup convertible to a carboxyl group. Suitable dienophiles areillustrated by acrylic acid, crotonic acid, acrylonitrile, alkylacrylate, alkyl methacrylate, acrylamide, N,N-dialkylcrotonamide and thelike. Among the suitable conjugated dienes are included cyclopentadiene,'butadiene, piperylene, isoprene and the like.

As mentioned previously, the epoxy alicyclic esters of this inventionare useful as plasticizers and as heat and light stabilizers for vinylhalide resins and as monomers for the preparation of valuable resins.For example, tris (2,3 epoxycyclohexylmethyl) 1,2,4 butanetricarboxylateis a good plasticizer for poly(viny1 chloride) and has merit as a heatand light stabilizer for this material.

The epoxy alicyclic esters are susceptible to polymerization by reactionof the epoxy groups. The polymerization can proceed by epoxy-epoxyinteraction, or by interaction of epoxy groups with other functionalgroups such as anhydride and active hydrogen groups. Compoundscontaining active hydrogen groups are illustrated by polycarboxylicacids and polyhydric alcohols and phenols. The epoxy alicyclic esterscontaining olefinic unsaturation, e.g., bis(2,3-epqxycyclohexyl) vinyl1-ch1oro-1,2,4-butanetricarboxylate, have the additional feature ofbeing polymerizable both through the epoxy groups and through the olefingroups. These two dissimilar groups react to form polymers by entirelydifferent reaction mechanisms. The olefinic epoxy ester can be subjectedto conditions whereby polymerization occurs through one kind of group tothe exclusion of polymerization through the other kind of group. Theresulting polymer then can be further polymerized under the properconditions through the unaffected second kind of group so that a morerigid, tougher resin is formed. For example, an unsaturated epoxy esterof this invention can be copolymerized with a vinyl monomer, such asvinyl chloride, to form a copolymer containing unreacted e-poxide groupswhich could then be cross-linked by treatment with acid or base toinduce reaction of the available epoxide groups. Or, on the other hand,an ester of this invention can be copolymerized with a monomer such asethylene oxide or ethylenediamine to form a copolymer which containsdouble bonds capable of cross-linking by treatment with a peroxide or byheat at an elevated temperature. The dissimilarity of thepolymer-forming epoxy and olefin groups enables control over polymerformation. so as to produce polymers having a great variety ofproperties.

The particularly preferred epoxy alicyclic esters of this invention,i.e., those containing at least one cyclohexene oxide group, haveoutstanding utility because of extraordinary reactivity of cyclohexeneoxide groups with carboxylic acids. Based on this unique reactivity, thecyclohexene oxide esters are valuable in the preparation of ester orvarnish-type coatings. It has been discovered that epoxy alicyclicesters of this invention containing at least two cyclohexene oxidegroups can be interacted with various fatty acids to form cyclohexeneoxide-fatty acid esters which can be applied as protective coatingshaving properties superior to the coatings prepared from conventionalepoxy materials. For example, tris (3,4-epoxycyclohexylmethyl)1,2,4-butanetricarboxylate can be reacted with an aliphaticmonocarboxylic acid such as dehydrated castor oil acid in an amountsuflicient to provide between about 0.3 and 0.7 carboxyl equivalents perepoxy equivalent of said polyepoxide and the resulting cyclohexeneoxide-fatty acid ester can be applied and cured on a substrate to form acoating having outstanding caustic and water resistance, toughness,flexibility, excellent color retention on exposure to ultraviolet lightand excellent resistance to the deleterious effects of outdoor exposure.Conventional drying-oil esters based on commercial epoxides arerelatively expensive and generally exhibit poor color retention onexposure to ultraviolet light, severe chalking on exposure to outdoorconditions and poor solubility in inexpensive solvents.

The following examples will serve to illustrate specific embodiments ofthe invention.

Example 1 A solution (281 grams) of 25.7 percent peracetic acid in ethylacetate was fed dropwise to 3-cyclohexenylmethyl bis(2-ethylhexyl)1,2,4-butanetricarboxylyate (456 grams) at a temperature around 50 C.over a period of one hour. After a reaction time of an additional fivehours at 50 0., analysis of the reaction mixture indicated that astoichiometric amount of peracetic acid had been consumed. The reactionmixture was stripped of ethyl acetate, acetic acid and excess peraceticacid by passing it through a steam-heated evaporator, first at 45 to 50millimeters of mercury pressure, then again at 4 to 5 millimeters ofmercury pressure, and finally at 1 to 2 millimeters of mercury pressure.3,4-epoxycyclohexylmethyl bis(2-ethylhexyl) 1,2,4-butanetricarboxylate(465 grams) was obtained as a residual product containing 2.75 percentoxirane oxygen (91 percent purity).

Example 2 A solution (208 grams) of 25.5 percent peracetic acid in ethylacetate Was added dropwise to bis(3-cyclohexenylmethyl) 2-ethylhexyl1,2,4-butanetricarboxylate (156 grams) at a temperature of 46 C. over aperiod of thirty minutes. After an additional four hours of reactiontime, volatile materials were removed from the mixture by passing itthrough a steam-heated evaporator in the same manner as in Example 1.Bis(3,4-epoxycyclohexylmethyl) 2-ethylhexyl 1,2,4-butanetricarboxylate(161 grams) was recovered as a residual product which contained 5.17percent oxirane oxygen (84 percent purity).

Example 3 A solution (251 grams) of 25.2 percent peracetic acid in ethylacetate Was added dropwise to 3-cyclohexeny1- methyl bis(oxo decyl) 11,2,4-butanetricarboxylate (448 grams) at a temperature of 50 C. to 55C. over a period of forty-five minutes. After an additional four hoursof reaction time at 50 C. to 55 C., volatile materials were strippedfrom the reaction mixture as in the preceding examples.3,4-epoxycyclohexylmethyl b-is(oxoi decyl) 1,2,4-butanetricarboxylatewas obtained as a residual product containing 2.4 percent oxirane oxygenpercent purity).

Example 4 A solution (565 grams) of 26.9 percent peracetic acid in ethylacetate was added dropwise to tris(3-cyclohexenylmethyl)1,2,4-butanetricarboxylate (337 grams) at a temperature of 50 C. over aperiod of one hundred five minutes. After an additional two hours ofreaction time at 50 C., volatile materials were removed from thereaction mixture as in the preceding examples. Tris(3,4-epoxycyclohexylmethyl) 1,2,4-butanetricarboxylate (396 grams) wasobtained as a residual product containing 6.98 percent oxirane oxygen.

Example 5 A solution (297 grams) of 27.1 percent peracetic acid in ethylacetate was added dropwise to bis(3-cyclohexenylmethyl) vinyl 1,2,4butanetricarboxylate (214 grams) at a temperature of 30 C. to 40 C. overa period of eighty minutes. After an additional four hours and twentyminutes of reaction time, volatile materials were removed from thereaction mixture as in the preceding examples.Bis(3,4-epoxycyclohexylmethyl) vinyl 1,2,4- butanetricarboxylate grams)was isolated as a residual product containing 6.2 percent oxiraneoxygen.

Example 6 A 20 to 30 percent solution of peracetic acid in ethylacetate, containing approximately 3.3 moles of peracetic acid, is feddropwise to tris(3-cyclohexeny1methyl) 1,2,4- cyclopentanetricarboxylate(473 grams) at a temperature of 5 0 C. over a period of approximatelyone hour. After an additional reaction period of one to six hours, whentitration of the excess peracetic acid indicates that the reaction isessentially complete, the reaction mixture is stripped of ethyl acetate,acetic acid and excess peracetic acid by passing it through asteam-heated evaporator in the same manner as in the preceding examples.Tris- (3,4-epoxycyclohexylmethyl) 1,2,4 cyclopentanetricarboxylate isobtained as a residual product.

Example 7 A solution of peracetic acid (20 to 30 percent by Weight) inethyl acetate, containing approximately 1.1 moles of peracetic acid, isfed dropwise over a period of about one hour to one mole of2-cyc1opentenyl bis(2- ethylhexyl) 1,2,4-butanetricarboxylate, at areaction temperature of 5 0 C. The reaction mixture is held at 5 0 C.for an additional one to six hours until analysis indicates that astoichiometric amount of peracetic acid has been consumed. The reactionmixture is stripped of ethyl acetate, acetic acid and excess peraceticacid by passing it through a steam-heated evaporator as in the precedingexamples. 2-3-epoxycyclopentyl bis(2-ethylhexyl) 1,2,4-butanetricar-boxylate is obtained as a residual product.

Alcohol prepared in the 0x0 process by reaction of tripropylene withcarbon monoxide and hydrogen.

'2 What is claimed is: 1. A compound of the formula hexylmethyl,3,4-epoxycyclohexyl, and 3,4-epoxycyclo- 1 hexylmethyl and at least twoR radicals are selected from the group consisting of2,3-epoxycyclohexyl, 2,3-epoxycyclohexylmethyl, 3,4-epoxycyclohexyl and3,4-epoxycyclohexylmethyl and the total number of carbon atoms in said Rradicals is between seven and about sixty carbon atoms.

2. Tris(3,4-epoxycyclohexylmethyl) tanetricarboxylate.

1,2,4 cyclopen- References Cited in the file of this patent UNITEDSTATES PATENTS 2,476,992 Shokal et al July 19, 1949 2,935,492 NeWey May3, 1960 FOREIGN PATENTS 559,078 Canada June 17, 1958

1. A COMPOUND OF THE FORMULA
 2. TRIS(3,4-EPOIXYCYCLOHEXYLMETHYL) 1,2,4 -CYCLOPENTANETRICARBOXYLATE.